CAD data exchange: Difference between revisions

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=== Neutral file exchange ===

Neutral file exchange uses an intermediary neutral format to translate data between CAD systems. This method starts from a pre-processor embedded in the original CAD system, which generates the neutral file from the originating CAD format. The target CAD system post-processes the neutral file and converts it into the target native format.<ref>{{cite journal |lastlast1=Choi |firstfirst1=G.-H. |last2=Mun |first2=D.-H. |last3=Han |first3=S.-H. |s2cid=11659726 |date=1 January 2002 |title=Exchange of CAD Part Models Based on the Macro-Parametric Approach |journal=International Journal of CAD/CAM |volume=2 |issue=1 |pages=13-2113–21 |url=https://pdfs.semanticscholar.org/13ca/477671832ff1d157cf17849876624da346d5.pdf}}</ref> Some neutral formats are defined by standards organisations such as [[IGES]] and [[ISO 10303|STEP]] while others are proprietary but still widely used and are regarded as quasi industry standards.<ref name=":15" />

==== Neutral formats ====

* [[IGES]] (Initial Graphics Exchange Specification) – originated in late 1979 and initially published by the American National Standards Institute (ANSI) in 1980 preceding the large-scale deployment of the CAD technology in the industry.<ref>{{Cite journal|lastlast1=Björk|firstfirst1=Bo-Christer|last2=Laakso|first2=Mikael|title=CAD standardisation in the construction industry — A process view|journal=Automation in Construction|volume=19|issue=4|pages=398–406|doi=10.1016/j.autcon.2009.11.010|year=2010}}</ref> This file format considers the product definition as a file of entities, with each entity being represented in an application-independent format.<ref name=":05" /> After the initial release of [[ISO 10303|STEP (ISO 10303)]] in 1994, interest in further development of IGES declined, and Version 5.3 (1996) was the last published standard.<ref name=":15" />

* [[AutoCAD DXF|DXF]] ([[Drawing Exchange Format|Drawing eXchange Format]]) – developed by [[Autodesk]] in 1982 as their data interoperability solution between [[AutoCAD]] and other CAD systems. The DXF is primarily 2D-based and its format is a tagged data representation of all the information contained in an AutoCAD drawing file, which means that each data element in the file is preceded by an integer number that is called a group code indicating the type of following data element. As most commercial application software developers have chosen to support Autodesk's native [[DWG]] as the format for AutoCAD data interoperability, DXF has become less useful.<ref name=":05" />

* [[VDA-FS]] ([[Verband der Automobilindustrie]] – Flächenschnittstelle) – created by the German Association of the Automotive Industry in 1982 as an interoperability method for free-form surfaces.<ref>{{Cite journal |doi = 10.1016/0010-4485(87)90208-9|title = Product data interfaces in CAD/CAM applications: Design, implementation and experiences|journal = Computer-Aided Design|volume = 19|issue = 3|pages = 158|year = 1987}}</ref> This format differs from other formats in that it only supports the communication of free-form curve and surface data with associated comments, but no other geometric or non-geometric entities. Therefore, it is limited to representations by parametric [[polynomial]]s, but this covers the great majority of free-form CAD systems. It includes [[Bézier surface|Bézier]], [[B-spline|B-Spline]] and [[Coons patch|Coons]] tensor product types of surfaces and corresponding curves.<ref name=":2">{{Cite book|title=Product Data Interfaces in CAD/CAM Applications|lastlast1=Nowacki|firstfirst1=H.|last2=Dannenberg|first2=L.|date=1986-01-01|publisher=Springer Berlin Heidelberg|isbn=978-3-642-82428-9|editor-last=Encarnação|editor-first=Prof Dr-Ing José|series=Symbolic Computation|pages=150–159|language=en|doi=10.1007/978-3-642-82426-5_13|editor-last2=Schuster|editor-first2=Dr-Ing Richard|editor-last3=Vöge|editor-first3=Dr-Ing Ernst}}</ref> The VDA-FS specification is released in the German Industrial Standard DIN 66301.<ref>{{Cite book|title=Product Data Interfaces in CAD/CAM Applications|last=Phebey|first=T.|date=1986-01-01|publisher=Springer Berlin Heidelberg|isbn=978-3-642-82428-9|editor-last=Encarnação|editor-first=Prof Dr-Ing José|series=Symbolic Computation|pages=176–183|language=en|doi=10.1007/978-3-642-82426-5_16|editor-last2=Schuster|editor-first2=Dr-Ing Richard|editor-last3=Vöge|editor-first3=Dr-Ing Ernst|chapter = The Implementation of the VDAFS Geometric Data Interface on Computervision's CDS 4000 CAD/CAM System}}</ref>

* PDES (Product Data Exchange Specification) – originated in 1988 under the Product Definition Data Interface (PDDI) study done by [[McDonnell Aircraft]] Corporation on behalf of the U.S. Air Force. PDES was designed to completely define a product for all applications over its expected life cycle, including geometry, topology, tolerances, relationships, attributes, and features necessary to completely define a part or assembly of parts. PDES can be viewed as an expansion of IGES where organizational and technological data have been added. In fact, the later PDES contained IGES. The development of PDES under the guidance of the IGES organization and in close collaboration with the [[International Organization for Standardization]] ([[ISO]]) led to the birth of [[Standard for the Exchange of Product model data|STEP]].<ref name=":05" />

* [[ISO_10303-21|STEP]] ([[ISO 10303]] – [[Standard for the Exchange of Product model data|STandard for the Exchange of Product model data]]) – the work with the ISO 10303 standard was initiated in 1984 and initially published in 1994, with the objective to standardize the exchange of product data between [[Product Lifecycle Management|PLM]] systems. It is a very comprehensive set of specifications covering many different product types and many life cycle phases. STEP uses the neutral ISO 10303-11 format, also known as an [[EXPRESS (data modeling language)|EXPRESS]] [[Database schema|schema]]. EXPRESS defines not only the data types but also relations and rules applying to them.<ref name=":15" /> STEP supports data exchange, [[data sharing]] and data archiving. For data exchange, STEP defines the transitory form of the product data that is to be transferred between a pair of applications. It supports data sharing by providing access to and operation on a single copy of the same product data by more than one application, potentially simultaneously. STEP may also be used to support the development of the archive product data itself.<ref name=":05" /> STEP consists of several hundred documents called [[List of STEP (ISO 10303) parts|parts]]. Every year new parts are added or new revisions of older parts are released. This makes STEP the biggest standard within ISO. The 200-series parts STEP are called Application Protocols (AP),<ref name=":15" /> with the specific parts directly related to CAD systems: